Nearly all of the fishing rods sold today are made from fiberglass reinforced plastic, generally referred to simply as fiberglass rods, or the recently introduced graphite fiber reinforced plastic, generally referred to simply as graphite rods. Most of these rods are tapered, tubular, and hollow. Variations in the "action" of the rod are achieved by differences in the diameter of the tube and of the wall thickness. And, nearly all rods are made of more than one piece for ease of storage and transport. The fiberglass or graphite reinforced plastice tube is called a rod blank. The rod blank is cut into the desired number of pieces and fitted with a ferrule at the cut ends to removably join the ends when it is desired to use the rod. The majority of rods are made of two pieces, the smaller diameter portion being called the tip section and the larger diameter portion being called the butt section, the two sections in use being joined by a ferrule.
There are four types of ferrules in general use--the metal ferrule, the blank-over-blank ferrule, the solid fiber-reinforced plastic ferrule, and the tubular, fiber-reinforced ferrule. The metal ferrule consists of friction fit mating male and female metal portions which are bonded to the adjacent ends of the butt and tip sections in a two-piece rod. The blank-over-blank ferrule requires two rod blanks that have matching tapers at the ends that are to fit together. The solid fiber-reinforced ferrule consists of a short tapered tubular fiber-reinforced portion that is bonded into the end of the butt section and fits into the large end of the tip section. The tubular, fiber-reinforced ferrule usually consists of a tapered, tubular, fiber-reinforced portion bonded onto the large end of the tip section into which the butt section fits, but may also be formed at the end of the tip section during the formation of the tip section. Each of these types of ferrules require a friction fit between male and female mating parts. This, of course, requires close tolerance manufacturing and the connection becomes less effective as the parts wear. Moreover, particularly in the case of the friction fit metal ferrules now in use, even if proper tolerances are maintained in manufacture, small amounts of sand or dirt between the mating surfaces may make it very difficult to separate the rod pieces at the ferrule without applying a force which can damage other parts of the rod. Finally, the external metal and fiber-reinforced ferrules now in use create a bulge in the rod which may be aesthetically displeasing as well as providing a raised surface across which the line may drag and reduce the length of the fisherman's cast.